(CNN) — Mitt Romney’s refusal to release tax returns in the critical years of his income accumulation has done little to dispel the legitimate concern that arises from hints buried in his scant disclosure to date: Did he augment his wealth through highly aggressive tax stratagems of questionable validity?

One relevant line of inquiry, largely ignored so far, is to examine what exists in the public record regarding his attitude toward tax compliance and tax avoidance. While this examination is hampered because his dealings through his private equity company, Bain Capital, are kept shrouded, there are other indicators.

A key troubling public manifestation of Romney’s apparent insensitivity to tax obligations is his role in Marriott International’s abusive tax shelter activity.

Edward D. Kleinbard

Romney has had a close, long-standing, personal and business connection with Marriott International and its founders. He served as a member of the Marriott board of directors for many years. From 1993 to 1998, Romney was the head of the audit committee of the Marriott board.

During that period, Marriott engaged in a series of complex and high-profile maneuvers, including “Son of Boss,” a notoriously abusive prepackaged tax shelter that investment banks and accounting firms marketed to corporations such as Marriott. In this respect, Marriott was in the vanguard of a then-emerging corporate tax shelter bubble that substantially undermined the entire corporate tax system.

via Did Romney enable company's abusive tax shelter? – CNN.com.